AMMONIA IN THE HUMAN BODY. 
407 
(31.) On another day 40 grs. of urea were taken. 
At 1 1^* 30“ A.M. 40 grs. of urea in 5 ounces of distilled water. 
At 1** 30“ p.M. 7 ounces of acid urine gave evidence of nitric acid by the starch test. 
At 5'“ 30“ p.M. nitric acid was present. 
Up to O'" 30“ A.M. In the total quantity passed nitric acid, in small quantity, was 
found by the starch test. 
In order to determine whether the same effect would be produced out of the body 
by combustion of the urea, some urea was dissolved in alcohol, the specific gravity of 
the solution =*851 ; it was burnt in a spirit-lamp ; the products of combustion were 
collected for one hour. The carbonate of potash solution was examined for nitric 
acid, and without any concentration it was found by all the tests. 
Thus, then, whether in the body or out of the body, urea, by oxidation, gives rise to 
nitric acid. 
In St. George’s Hospital the urine of two patients with dropsy and albuminous 
urine, in whose blood urea might be considered to be probably present, was examined 
for nitric acid. In each case a pint of the urine was boiled, filtered and distilled, but 
no trace of nitric acid was found. In one case the experiment was repeated with two 
pints of urine, but still only a negative result was obtained. 
These experiments with urea showed that when small quantities were taken no 
nitric acid could be detected ; this led me to suppose that a large dose of the alka- 
loids would be necessary to produce any decided effect on the urine, and on this ac- 
count no alkaloid was taken. 
Caffein, however, was dissolved in alcohol, and when burnt for one hour in a spirit- 
lamp, it gave rise to nitric acid. 
As it appeared from these experiments that nitric acid was produced more readily 
and frequently than has been supposed to be the case, I was led to try whether com- 
bustions in the atmosphere, without ammonia, could not give nitric acid. 
I first tried the products of the combustion of alcohol. The spirit-lamp was used as 
before, and the products of combustion were passed through a solution of pure car- 
bonate of potash. The alcohol had not the slightest alkaline reaction, but after an 
hour’s combustion nitric acid was proved to exist in the carbonate of potash, by the 
starch test, and by the indigo test also. 
As it was possible that a small quantity of ammonia might have been present in 
the alcohol, I determined to collect the product of hydrogen burnt in the air. The 
gas was generated by pure sulphuric acid and distilled water, and it was burnt for 
one hour; nitric acid was found to be present in the carbonate of potash in small 
quantity*. 
The combustion of coal in a small furnace was then made, so that the products 
* After this paper was written, I found that Satjssure had described a similar experiment in the Annales 
de Chemie for 1809, vol. Ixxi. p. 285. Nitric acid and ammonia were detected hy him after the combustion 
of hydrogen gas in atmospheric air. 
3 G 2 
